Safety link



R. L. HHLER SAFETY LINK Feb. 15, 1949.

Filed May 9, 1945 2 Sheets-Sheet l /l/s ATTORNEYS Feb. 15, 1949.

Filed May 9,. 1945 R. L. HOHLER SAFETY LINK 2 Sheets-Sheet 2 INVENTOR Ruben LHUhZE'r l//s ATTORNEYS Patented Feb. 15, 19419 UNITED STATES FATENT' OFFICE SAFETY LINK Robert L. Hohler, Daytony Ghio Lapplicationv May 9,* 1945, Serial No. 592,849

(Cl. 20G-w35) 6 Claims. l This invention relates tosafety linlrs and/more particularly to links to prevent overloading hoists and electric hoisting apparatus.

In the use of electrical'. hoisting apparatus by which objects are raised or moved, as in manufacturing plants handling metals or otherheavy objects, accidents and injuries sometimes. occur to workmen as well as considerable damage to equipment due to the fact that failure' occurs` Another object of the present` inventiony is to provide a link which can be calibrated to suit a particular operation, not necessarilythe maximum capacity of the hoist. This is accomplished by having the switch mounted relative' to an: ad- ,iustable arm which actuates the switch;` The'link' is then calibrated by elongating-same to' a given load and then securing thc-:farm cooperate the switch at thisl load.

Another object of the present invention istok provide a link with an electrical switch therewith which may be operated at a predetermined load to open a circuit to the control device of theV hoiste ing apparatus when said predeterminedload is reached and at the same time so designed and arranged that the switch will not be actuated when load is below the predetermined load.

A more specific object of the present invention is to provide an elongated loop spring with a sensitive switch mounted thereon and connected electrically to the hoist controls which may be operated at a predetermined load to open cirn cuit to the electrical control device for the hoisting device. The switch is mounted in amanner thatat a predetermined load or overload applied to the cable the link will elongate a certain amount causing the switch to be actuated and open the circuit to the hoist controls. The link is calibrated to elongate a certain amount with a. given load oriwhen an obstruction is encourir tered before theswitch is operated soithat there is no danger of the switch being operated too soon to stop the hoisting apparatus When saferloads are being lifted.

FurtherV objects and advantages' of the present invention will be apparent from the following description, reference being made to the accompanying drawings wherein a preferred embodinient of the present-invention isiclearlyshown'.Y

In the drawings:`

Fig. l i's'an end view of the link embodyingA the present invention;

is a side View lookingin' the direction of arrow 2 in Fig. l.

Fig. 3 is an endviewof a modified form of the present invention.

Fig. 4 is a sideview looking inithe direction of arrow t in Fig; 3.

Fig. 5' is a sectional view taken on line 3-3'of Fig'.v

Fig. 61is a. sectional view'of'the switch.

Figi's alfragmentaryplan View of a modified' iorrn'of spring member;

Fig. Srisa"y sectionai view taken inline 3'-8 of Fig; 7.

Referringlto' Figs. l and 2, Zil designates a link device includingl attachment blocks 2|' and tapered openingS-to receive aleaded endl24"of a cable 25 while block 22 isv provided with a closedeye 2| couldbe formed' with a-olosedreye to receive a hook (not shown) pivotally suspended from a sta-- tionaryv member ssociated' with the hoist a10- paratus.K

A pair of preformed spring members Sil-andSl having bowed portions iii-and 33; respectively,l are secured von opposite sidesoi` the blocks 2i and 212 by bolts Sil. Itis to beunderstoodthat.any/'nume ber'oi-springinenibers canvbe used: Each bolt Ahas a shanlrpassing-through aligned apertures provided by the blocks and the ends ofthe spring members; Each bolt has a head-engagingfa spring or lock;y washer 35 engaging the outer face of spring member (it, and a nut tlengagingva soring or loclrwasher 3l engaging the outer face or. the:

spring member l l. Bysetting the nuts, the'springmembersv 3e and (il are securely` attached to the when tension is applied totheends thereof and longitudinally ofhthe spring the sides will move transversely andapproach eachother. It is to be understood that thespring members couldbe mounted so that thebowed portion may be reversed from thatshown in the drawings.

The block 2l inthis instance isprovided on one The block 2lin' this instance is=provided witha t is to be understood thatthe block end thereof with a longitudinal groove 45 to receive one arm 42 of an adjustable L-shaped bracket 4|. A screw 43 which passes through an elongated slot 44 in the arm 42 which will, when tightened, secure the bracket 4i to the block 2l in the desired position yof adjustment. The other arm 45 of the bracket 42 extends between the spring member. l

Mounted upon the lower side of the block 22 is an electric switch 50 of the snap-acting type. One form of switch construction and arrangement of .elements is shown in Fig. 6. It is to be understood other forms could be used. In the switch shown the switch comprises a base i closed by a cover 52 for enclosing the switch mech- ,y

anism. A threaded insert 53 is embedded in the base. A screw 54 having a threaded engagement with the insert 53 secures an anchor washer The insert provides an electrical connection between the washer 54 and an external screw 55. The washer 55 supports a snap-acting element or contact member 51 which when pressure is applied at 57a the element moves with a snap action between a stationary contact 58 and a nonconducting abutment 59 carried by the base made of insulating material. The contact 58 is electrically connected with an insert 55 embedded in the base, said insert 6|] provides an electrical connection between the stationary contact 58 and the external screw 6|.

The element 51 is mounted in cantilever fashion by the screw 54 and the element is constructed so that when pressure is applied to the element 51 at 51a by a plunger 62 slidably supported in a guide opening provided by the cover 52 the element 5i will snap into engagement with the stationary contact 58, but when said pressure is released the element will snap out of engagement with the stationary contact 5B. Fig. 6 shows the relative position of the element 51 after the pressure has been applied. Since any type of snap-acting switch construction can be used with the link, specic detailed description of the switch parts is deemed unnecessary. The switch 5G is enclosed within a protecting metal cover 63, said cover is held in position by screws 64. The screws 64 pass through holes in the base and have threaded engagement with tapped holes provided by a bracket 65.

Before the cover 53 is secured in position, one end of leads 65 and 61 are electrically connected with inserts 53 and 60 by screws 55 and 6| respectively. These leads BEE-5l preferably extend out through a rubber grommet or the like with the other ends thereof connected with respective terminals, not shown, of a suitable control switch for controlling the up'or lifting operations of the hoist apparatus, l

With the parts arranged as shown in Fig. 1 the upper end of the loop spring member is attached to a fixture while the lower end isattached to a cable 25 so that when a predetermined load is to be lifted bv the cable the lateral movement of the sides will not be suiiicient to permit the arm 45 to move far enough to allow the switch 5B to operate, thus the load can be lifted with safety. When, however, obstructions are encountered or excessive loads are tried to be lifted by the cable 25 the cable `will pull the block 2| downwardly against the tension of the springs and 3i causing the bowed portions 32 and 33, respectively, of the springs 35 and 3| to approach each other. This downwardmovement of the block 2| carries the bracket 4| with it, thus when the block has moved a certain distance downward,

Col

a other suitable manner.

as viewed in Figs. 1 and 2, the element 51 will snap out of engagement with the stationary contact 58 to open a circuit to an up-control switch (not shown) for the hoisting apparatus. When the overload has been relieved the link-switch will automatically close thus permitting the up-control switch to be reset. It is to be understood that the links can be mounted in many other ways so long as the link proper is arranged to permit elongation thereof. For example, when a chain is used the link can be mounted between the hoist dollies or hanger and the hoist proper.

If desired the link may be enclosed within a steel casing S8. The top wall 69 and the bottom wall 59a have notches through which the eye 26 and cable 25 project. The bottom wall 59a acts as a stop to limit the amount of movement of elongation of the link.

In the modiiied form shown in Figs. 3, 4, 5, and 6 a link comprises a set of spring members I0 and 'il having bowed portions 'l2 and 'i3 respectively. The opposed ends of the spring members engage each other and said ends together with suitable plates are secured together by welding or in any In this present instance apertured plates 'i4 and a pair of semi-circular members 25 are arranged on opposite sides of the spring ends and welded together. The plate ends are provided with apertures which align with the apertures in the ends of the spring members 1E!- said apertures receiving a cable, hook or shackle attached to a stationary element. The lower ends of the spring members 'I0-'ii are also secured together by welding two apertured washers or plates disposed on opposite sides of the ends. The apertures of the plates align with the apertures provided by the spring ends to receive a cable. The cable is threaded through the apertures and then clamped in any suitable manner such as a U-bolt. The bowed portion l2 of the spring member 'i8 supports a switch 59 having the biased plunger 62 while the bowed portion 'I3 of the spring member 7|! supports an adjustable screw I6 having a tapered end 'i1 normally spaced from the end of the actuator 52 located outside the cover 52. The screw is held in an adjustable position by a lock nut 82,

With the' parts as thus arranged, Ias viewed in Fig. 3, the upper end of the link when attached to a xed part, not shown, and the lower end to a cable 25, any normal strains, while tending to cause the bowed portions 'l2 and 'i3 to approach each other will not be suicient to cause the tapered portion of the screw to actuate the plunger 52. However, when an excessive load is attempted to be lifted or an obstruction is encountered the bowed portions 'l2-'I3 will approach each other suiiiciently to cause the tapered portion of screw 'Vl to cam the plunger inwardly to apply pressure at the point 52a to cause the element 5'! to move with a snap action to move same out of engagement with the stationary contact 58 and engage the abutment 59.

Referring to Figs. 7 and 8 a fragment of a rnodied form of arced shaped spring members 82 adapted to be connected to blocks 2| and 22 is shown. When this type of spring member is used. the blocks 2| and 22 are provided with extensions or lugs 90. Each spring member is hingedly connected with the blocks 2| and 22 by hinge pins or bolts 9| around which ends of the spring member are bent.

In the operation oi the link devices thus described, it will be assumed that the link switch is connected electrically with a locking type relay switch with a reset feature and the relay is in turn connected in series with the electrical 11p-control device for the hoist apparatus. Let it further be assumed that the link switch is associated with a 1000 pound capacity cable hoist. On a 1000 pound capacity hoist with a one sheave load block, the link can be set for 750 pounds which will give a 1500 pound capacity maximum loading. That is, when a load is lifted effecting a 1500 pound or more on the spring link, the link will elongate causing the spring link switch to operate to open the circuit to the lock out relay switch which in turn will break the circuit to the up-control device of the hoist. The down-control position of the control device for the hoist will not be effected. Thus, the down control of the control device can function to relieve the overload. When the overload has been relieved, the lock out switch can be reset to put all of the switches in their normal positions. By this arrangement the operator must call an electrician to reset the lock-out relay. It is to be understood that the lock-out relay switch could be omitted.

While the embodiment of lthe present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. A safety link apparatus comprising, a set of preformed spring members; means for securing the ends of the spring members together to form a loop with the sides thereof adapted to move relative to each other under tension, one end of the loop adapted to be attached to a stationary member while the other end is adapted to be connected to a means capable of lifting a predetermined load; a switch carried by one of the spring members for -controlling a circuit, said switch including a relatively stationary contact and a movable contact arranged in a certain relation when the spring members are in their normal position; and an adjustable plunger for the switch carried by the other spring memiber, said spring members moving relative to each other when the spring members are subjected to stresses equal to or yabove the adjusted setting of the plunger to cause the plunger to change the relation of the contacts due to elongation of the spring members.

2. A safety link apparatus comprising, an elongated spring member having spaced sides capable of moving toward each other under tension, one end of the Aspring member Icapable of being xed to a stationary member and the other end adapted to be attached to a movable member; a switch having a biased lcontact 'and a relatively stationary contact carried lby the spring member; adjustable means carried by the spring member for holding the movable contact in engagement with the stationary contact to complete a circuit, said adjustable means adapted 6 to be moved by the elongation of the spring member when the spring member is subjected to abnormal stresses and thereby permit the biased contact to move out of engagement with the stationary contact by its own resiliency.

3. A safety link apparatus comprising, a plu` rality ci bowed leaf springs; a pair of spaced blocks; means for securing opposite ends of one or more leaf springs to opposite sides of the blocks to form a closed loop, said spring being capable oi moving relative to each other under stress, one end of the loop adapted to be attached to a sta-- tionary member while the other end is adapted to be affixed to a means capable of lifting a predetermined load; a switch carried by the loop, said switch including a stationary contact, a biased Contact, and a plunger; an adjustable bracket carried by the loop and having an arm engaging the plunger causing same to hold the biased contact into engagement with the stationary contact when the load is at or below the predetermined load said springs moving relative to each when an excess load is imposed upon the loop to move the arm from the plunger and permit the biased contact to move out of engagement with the stationary contact to open the circuit; andvmeans for limiting the movement of the leaf spring.

4. A safety link according to claim 3 in which the opposite ends of the bowed leaf spring members are hingedly connected on opposite -sides of the block.

5. A safety link apparatus comprising; in combinat1on a relative stationary member; a relative movable member; a plurality of bowed leaf springs arranged in parallel; means for securing opposite ends of the leaf spring to the members; an elec'- tric switch; means for supporting the electric switch for actuation by relative movement of the members; and means actuated upon flexing of the leaf springs for actuating the switch.

6. In an electrical hoist apparatus, the combination comprising; a safety link for connecting a load to a hoist apparatus, said link including a relative fixed member and a relative movable member; bowed spring members arranged in parallel to connect the fixed member with the movable member and adapted to flex upon application of load to the link; an electric switch device for indication of overload; means for supporting the switch device so as to be actuated upon flexing of the springs; and means operated by applying the load to the link for actuating the switch.

ROBERT L. HOHLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,613,215 Albersheim Jan. 4, 1927 2,389,103 Wood Nov. 13, 1945 

